Quick Answer: The two most common types of residential foundation wall construction in San Jose are poured-in-place concrete and CMU (Concrete Masonry Unit) block. Poured concrete is the stronger, more monolithic option — it has no mortar joints, handles seismic loads better, and is the standard for new construction in California. CMU block (also called “cinder block”) was common in Bay Area homes built from the 1940s-1970s — it’s structurally adequate if the mortar joints are intact and the blocks are not cracked, but tends to be more susceptible to water infiltration through mortar joints and is generally considered inferior to poured concrete for seismic zones. If your San Jose home has a CMU foundation and you’re planning a renovation or addition, a structural engineer should evaluate the foundation for seismic adequacy before you expand on top of it.
CMU Block vs. Poured Concrete Foundation Comparison
Helpful Resources:
| Feature | Poured Concrete | CMU Block |
|---|---|---|
| Seismic performance | Excellent (monolithic) | Moderate (mortar joints are weak point) |
| Water resistance | Good (no joints) | Moderate (mortar joints can leak) |
| Common in Bay Area | Post-1980 construction | 1940s-1970s homes |
| Repair difficulty | Moderate (core drill for repairs) | Easier (replace individual blocks) |
| Strength | 3,000-5,000 PSI typical | 1,900-2,500 PSI typical |
| Seismic upgrade complexity | Low (most modern poured foundations meet code) | Higher (may need bolt anchors, epoxy) |
Quartz Construction provides foundation evaluation and seismic retrofit services for San Jose homes with both CMU block and poured concrete foundations. Learn about our foundation services. CSLB #1003436 | Call (650) 749-7436.
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